Is my solution correct? About momentum

Block 1 (mass 6 kg) is moving rightward at 8.0m/s and block 2 (mass 4 kg) is moving rightward at 2.0m/s. The surface is frictionless and a spring with a spring constant of 8000N/m is fixed to block 2. Eventually block 1 overtakes block 2. At instant block 1 is moving rightward at 6.4m/s, what are (a) the speed of block 2 and (b) the elastic potential energy of the spring?